required attribute %1 not specified

Cause:

The attribute given above is required for an element that you've used, but you have omitted it. For instance, in most HTML and XHTML document types the "type" attribute is required on the "script" element and the "alt" attribute is required for the "img" element.

Example:

textexample textexample

Bad:
textexample textexample
Good:
textexample textexample

Solution:

textexample textexample

References: